A comparative study of single-channel signal processing methods in fetal phonocardiography

Abstract

Fetal phonocardiography is a non-invasive, completely passive and low-cost method based on sensing acoustic signals from the maternal abdomen. However, different types of interference are sensed along with the desired fetal phonocardiography. This study focuses on the comparison of fetal phonocardiography filtering using eight algorithms: Savitzky-Golay filter, finite impulse response filter, adaptive wavelet transform, maximal overlap discrete wavelet transform, variational mode decomposition, empirical mode decomposition, ensemble empirical mode decomposition, and complete ensemble empirical mode decomposition with adaptive noise. The effectiveness of those methods was tested on four types of interference (maternal sounds, movement artifacts, Gaussian noise, and ambient noise) and eleven combinations of these disturbances. The dataset was created using two synthetic records r01 and r02, where the record r02 was loaded with higher levels of interference than the record r01. The evaluation was performed using the objective parameters such as accuracy of the detection of S1 and S2 sounds, signal-to-noise ratio improvement, and mean error of heart interval measurement. According to all parameters, the best results were achieved using the complete ensemble empirical mode decomposition with adaptive noise method with average values of accuracy = 91.53% in the detection of S1 and accuracy = 68.89% in the detection of S2. The average value of signal-to-noise ratio improvement achieved by complete ensemble empirical mode decomposition with adaptive noise method was 9.75 dB and the average value of the mean error of heart interval measurement was 3.27 ms.

Adopting Artificial Intelligence Algorithms for Remote Fetal Heart Rate Monitoring and Classification using Wearable Fetal Phonocardiography

“…From the above equation, env(i) denotes the signal envelope, r ′ (i) 2 actual signal (i.e., the real part), and r ′ ̂(i) 2 is the Hilbert transformed signal (i.e., the enveloped signal). Eventually, the LPF was used to smooth the incoming signal based on the cut-off frequency.…”

“…In the 15th century, monitoring the infant's pulse for medical purposes was first introduced, but was not formally accepted. It was not until the mid 19th century that this practice of heartbeat detection through auscultation was officially validated [1], [2]. Initially, a stethoscope was used to monitor the rate of the beats.…”

“…Numerous methods have been developed in recent years to address this issue [3], [4]. Such methods include... via microphones [9] FCTG is a widely used practice for monitoring fetal heart rate (FHR); however, it faces the major drawback of radiation exposure due to ultrasound [10]. FMCG is a non-invasive technique that offers improved signal morphology and increased signal-to-noise ratio (SNR), albeit at a high cost and necessitating a special precaution room to reduce magnetic signal radiation [11].…”